Re: lens choice for high res video camera

In article <1122246523.577168.221430@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"buster" <buster_googlegroups@xxxxxxxxx> wrote:

> Thanks for your answer! To start with your last comment:
> >It would probably be worth your while to have someone with the appropriate
> >experience check out your setup in detail because there may be other
> >issues that would affect your results.
>
> Before I place the order an optics-specialist who is currently not
> available will review my work. For now I try to learn of it as much as
> possible.I found a lot of usefull information at the website of
> edmundoptics:
> http://www.edmundoptics.com/techSupport
> And particullary "optics":
> http://www.edmundoptics.com/techSupport/DisplayCategory.cfm?categoryid=15
> and "Machine Vision"
> http://www.edmundoptics.com/techSupport/DisplayCategory.cfm?categoryid=18
>
> Back to your comments:
> >Well, your focal length calculations are close. The actual theoretical
> >focal length for the desired reduction at 600mm WD is 21.9mm because you
> >have to extend the lens to focus. But a 25mm will work fine; the front
> >focal distance (which is generally going to be different from the
> >working distance) is actually 685mm.
> Can you give me the formula how you calculate this (or a link)

Bob May has provided the formula.

> >You may have a better chance of getting a 25mm in C-mount than F-mount
> >since the latter is a 35mm standard and most of the lenses are made to
> >cover a 43mm circle.
> Do you mean by "cover a 43mm circle" the projected circle which should
> cover the complete CCD area?

Yes. For example, your 15X15mm CCD requires a lens that covers a 21.4mm
circle. It is easier to make a 25mm lens cover a 21mm circle than a 43mm
circle.

> >There are a lot of 24mm F-mount lenses but they're
> >wide angles and commonly do have some distortion. The distortion over
> >the area of your sensor, though, should be very low.
> So I shouldn't go for a 24mm F-mount. Or do yoy mean with this last
> sentence that it's not a problem to use one?

I mean I don't know. I would have to look at the distortion
specifications of any given lens to see how it is over the area of
interest. The 24mm f/2 Nikkor, for example, may be found to be suitable.

> >You can get very fast (low f/number) 25mm C-mount lenses but a lot of
> >them are low quality and designed for small sensors. You need a good
> >lens that will resolve the 7 micron pixel pitch of your sensor and cover
> >a 21mm circle. The only one that comes to mind is the Rodenstock f/4
> >enlarging lens but there should be others.
>
> Is this the Rodenstock f/4 you mention:
> VIDEO LENS- RODAGON 28MM FL
> http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1416

Yes. This is a very sharp, distortion-free lens.

> Edmund Optics also advises this "rodagon" lens for the "Redlake
> MegaPlus Cameras". The 4MP version (ES-4020)of these family has the
> same CCD (is this a 1"?) as the Adimec 4020m which is equiped with a
> F-mount (?)
>
> Can you tell me how I have to read the tables at this link:
> http://www.edmundoptics.com/onlinecatalog/DisplaySpec.cfm?productid=1416#ES402
> 0

I can't make sense of the tables. It appears that a Rodagon plus a
focusing tube will fit to a C-mount camera and let you focus on your
work without needing a spacer. An F-mount camera will need an F-mount
adapter.

> >What concerns me is that you stated:
> >"I know that a small lens diameter in combination with a large sensor
> >size and a large aperture (diaphragm) gives a lot of distortion."
> What I meant the above in combination with the setup I need (relative
> large FOV and short working distance)
>
> Can you tell me also something about the depth of field I get with the
> f/4 lens you suggested?
> Should I equip my lens-camera system with an iris (aperture)?

Depth of field depends on the allowable unsharpness in the image plane.
For a 15 micron circle of confusion (the diameter of the unfocused beam)
you will have a depth of field of 52mm at a 600mm distance with a 28mm
lens. If you have a 24mm f/2 the depth of field is 36mm (See

http://bobatkins.com/photography/technical/dofcalc.html#calc
)

These lenses typically have internal aperture diaphragms.
.

Relevant Pages

  • Re: lens choice for high res video camera
    ... your 15X15mm CCD requires a lens that covers a 21.4mm ... >>>wide angles and commonly do have some distortion. ... >> So I shouldn't go for a 24mm F-mount. ... > These lenses typically have internal aperture diaphragms. ...
    (sci.optics)
  • Re: Which hurts images more, shift lenses or correcting perspective in software?
    ... distortion via a shift or tilt-and-shift method is preferable to ... It's true that a tilt-shift lens is a physical device which operates ... What a tilt shift lens does is to allow you to change the relative ... transformations along x and y axes. ...
    (rec.photo.digital.slr-systems)
  • Re: Progressive Lens Choices
    ... I do know of a "Guild" optician in my area. ... distortion that needs to be minimized. ... changing from SV to a +2.00 Add PAL (progressive addition lens), ... single design can meet all these requirements optimally at once? ...
    (sci.med.vision)
  • Re: Which hurts images more, shift lenses or correcting perspective in software?
    ... the 3- D distortion before it is projected onto the "film ... wide-angle lens, used to take multiple photos, and stitching ... You may be right, although the taking and later stitching, no ... A side note for my hobby of car pictures. ...
    (rec.photo.digital.slr-systems)
  • Re: Good Wide Lens for Digital Rebel XT
    ... Assuming that we're talking about real distortion here, ... I'm quite frankly amazed at what can be done with images with this ... I wonder if some lens manufacturer will ever produce ... Photography Review has a lot on this lens: ...
    (rec.photo.digital.slr-systems)